function NPC(x, y, width, height, activity){
	this._activity = activity;
	NPC.superclass.constructor.call(this, x, y, width, height);
	this.draw = function(context){
		context.fillStyle = "navy";
		context.beginPath();
		context.rect(this._x, this._y, this._width, this._height);
		context.closePath();
		context.fill();
	}
}
extend(NPC, Unit);